Add high-fidelity landing page hero section

[Adeolu01]

Summary

Implements the desktop landing page hero section based on the Dark Mode design, following the project's Component -> Hook -> Service architecture.

• Navigation bar with logo wordmark and primary nav links (Product, Fleet, Pricing, Docs), plus Sign In CTA and a mobile menu affordance
• Responsive hero typography that scales from mobile through desktop breakpoints
• Animated statistics counters that count from zero to their target value using Framer Motion (useInView + useMotionValue/useSpring), triggered once the section scrolls into view
• Primary CTA button labeled "Secure Your Shipment"

Architecture

• Service: services/landingService.ts - getHeroStats(), axios-based, follows the existing faqService.ts pattern
• Hook: hooks/useHeroStats.ts - useQuery wrapper returning stats plus loading/error state
• Component: components/landing/HeroSection.tsx - consumes useHeroStats() only; stat counters render as skeletons while loading rather than fabricating numbers

Integration

• Replaced the inline hero section in app/page.tsx with HeroSection; the rest of the landing page is unchanged

Testing

• npx tsc --noEmit: no errors in files touched by this change (pre-existing unrelated errors elsewhere in the repo are untouched)
• npx eslint on the changed files: 0 errors, 0 warnings
• Manually verified counter animation, responsive typography, and nav focus states

Notes

• Backend endpoint /api/landing/hero-stats is assumed per the issue spec. Until it exists, the stat cards render as loading skeletons.
• The mobile menu button is present for layout completeness but does not yet open a drawer; the issue scope covers the desktop hero and did not require full mobile nav behavior.

closes #307